This application claims the benefit of German patent application no. 10056076.8, filed Nov. 7, 2000, herein incorporated by reference.
1. Field of the Invention
The invention relates to an improved housing for a thermostatic valve for a coolant circuit of an internal combustion engine, which housing is formed at least partially of a plastic material, and in which housing electrical connecting leads are embedded.
2. Background of the Invention
In a thermostatic valve for a coolant circuit of an internal combustion engine, it is advantageous to be able to control the operation of the valve other than through the temperature of the coolant flowing through the valve. One means by which the operation of a thermostatic operating element for such a valve may be controlled is by the inclusion of a heating element within the thermostatic operating element, which heating element is controlled electrically from the exterior of the valve.
The desire to maintain electrical control over the heating element presents a substantial conflict between the need to have electrical leads enter into the valve housing and the need to prevent coolant from leaking through the point of entry of the electrical leads. For instance, German Patent Appl. No. DE 42 33 913 A1 teaches a housing for a thermostatic valve for a coolant circuit of an internal combustion engine in which the electrical leads supplying a heating element of a thermostatic operating element within the valve housing run from the heating element to a point outside the valve housing. Specifically, the housing of the thermostatic operating element is mounted on the valve housing and the electrical leads are embedded in a plastic casing of the housing of the thermostatic operating element. The electrical leads are directed through a conduit within a crosspiece of the valve housing, upon which crosspiece the thermostatic operating element is supported, and to the exterior of the valve housing. Because coolant flows within the valve housing, around the thermostatic operating element and the crosspiece on which it is supported, this configuration necessitates a substantially perfect seal between the interior of the valve housing and the conduit, lest coolant leak from the system through the conduit.
Moreover, in order to facilitate the connection of the electrical leads to a plug socket to be mounted on the outer wall of the valve housing, the electrical leads must be longer than the conduit within the crosspiece. When the plug socket is mounted to the outer wall, the excess length of the electrical leads must be pressed into the conduit, thereby resulting in slack in the electrical leads. This slack causes the electrical leads to be susceptible to vibrations, which can result in movement of the supply leads, unwanted noise, or damage to the supply leads-in any event, sub-optimal performance of the system.
It is accordingly an object of the present invention to improve upon prior-art thermostatic valves, in order to ensure a greater level of manufacturing and operational reliability.
In order to meet this object, the present invention includes a housing of a thermostatic valve for a coolant circuit of an internal combustion engine, which housing is formed at least partially of a plastic material. During the manufacturing process of the housing, electrical leads for supplying electricity to a thermostatic operating element are injected or cast into the housing. Because the electrical leads are embedded in the plastic material, they remain in a fixed position, which eliminates the rubbing or flapping associated with movement of slack electrical leads in a conduit and the resulting noise or damage. Moreover, embedding the electrical leads in the plastic material eliminates the need for an additional seal, since there is no conduit for coolant to leak through. An additional benefit of the present invention is that the plastic material insulates the electrical leads; no additional insulation of the electrical leads, as would be needed in a conduit system, is required. Consequently, the thermostatic valve of the present invention is both operationally reliable and economical to manufacture.
An additional feature of the present invention is the ability to form electrical connectors, such as contact tags or sockets, in the plastic portion of the valve housing. By selecting electrical leads of a shape appropriate for placement within an electrical connector and forming the insulating/connecting portion of the electrical connector as part of the valve housing, a mechanically loadable electrical connector may be formed and placed without any additional work steps, thereby reducing the cost of manufacture.
In accordance with this feature of the present invention, part of the portion of the value housing projects into the interior of the valve and into the coolant flow path to form a support. The electrical leads are embedded within this projection, at the end of which is formed a receptacle that includes an electrical connector and a support upon which is mounted, depending on the particular configuration of the valve, the housing of the thermostatic operating element or the work piston of the thermostatic operating element. Because the electrical leads are sealed within the projection, no further sealing mechanism is necessary despite the placement of the projection within the coolant flow path. Moreover, the embedding of the electrical leads and the forming of the electrical connector and support for the thermostatic operating element may be accomplished simultaneously with and as part of the manufacturing process for the valve housing. In one embodiment of the present invention, the receptacle is formed with a circumferential wall that defines a recess, on the bottom of which the electrical connectors are arranged. The contact pins of the work piston or of the heating element are inserted into the electrical connectors, and the thermostatic operating element is thereby seated on the projection.
In another embodiment of the present invention, the outer wall of the valve housing is formed with a receptacle, in which electrical connectors of the connecting leads are embedded, and which is adapted to receive an external power source. In accordance with this embodiment, a plug receptacle for connecting an external electrical supply to the valve is integrated within the valve housing, thereby eliminating the need for a separate manufacturing step or separate structural components in order to provide a suitable receptacle.
In still another embodiment of the present invention, the electrical leads are formed from substantially planar conducting strips instead of conventional wires. Conducting strips, also known as current bars, provide a number of substantial advantages over conventional wires when used in the system of the present invention. For instance, conducting strips, by virtue of their planar design, are inherently more stable than are conventional round wires when injected into plastic material during the manufacturing process of the housing. The conducting strips are easily bent into a particular configuration in order to achieve a desired shape. Moreover, rotating the strips about their longitudinal axes serves to anchor them firmly within the plastic material.
Further features and advantages of the invention result from the claims and the following description of preferred embodiments of the invention in conjunction with the drawings.